1. Field of the Invention
This invention relates to a chip resistor, and more particularly to a lead-less chip resistor which is adapted to be mounted as a chip-type electronic element on a printed circuit board.
2. Description of the Prior Art
Conventionally, a chip resistor has been typically manufactured in a manner to form a resistance element or film on a chip-like insulating substrate by screen printing and then form end electrodes on both side end surfaces of the substrate. The end electrode has been conventionally formed according to a thick film deposition technique. More particularly, it is formed, for example, by applying Ag--Pd to the substrate and baking it, and then applying Ni, Pb--Sn (Sn) or the like thereto by plating. Accordingly, the conventional chip resistor is called a thick film-type chip resistor. Supply of such a chip resistor to a consumer is generally carried out by means of a chip charging magazine or chip carrying tape.
Manufacturing of the conventional chip resistor according to the thick film deposition technique, as briefly described above, is carried out by forming the resistance film on a single insulating substrate material by printing and baking, dividing the substrate into bar-shaped sections, carrying out application and baking of Ag--Pd on each of the bar-shaped sections to form the end electrodes thereon, and then dividing each of the bar-shaped section into chip units followed by plating of Ni, Pb--Sn (Sn) or the like on each of the chips, to thereby obtain the chip resistor.
Unfortunately, the conventional chip resistor manufactured as described above has a disadvantage that a failure in application of Ag--Pd on the substrate with high precision fails to provide configuration and dimensions of the final product with good precision. Also, baking of Ag--Pd causes a variation in resistance of the resistance film baked in the previous step and deteriorates temperature and high frequency characteristics of the resistance film. Further, the plating is carried out by immersing the chip in an acid or alkaline plating solution, accordingly, a failure in control of the plating highly adversely affects reliability of operation of the final product. Furthermore, the conventional chip resistor causes its manufacturing process to be highly complicated and troublesome because the operation of dividing the substrate material into the barlike sections is highly difficult.
In the conventional thick film-type chip resistor, as described above, a variation in resistance of the resistance film often occurs and temperature and high frequency characteristics of the resistance film are readily deteriorated. In order to avoid such disadvantages, the inventors tried to form the resistance film according to a thin film deposition technique such as sputtering, vacuum deposition, ion plating or the like. However, this failed to provide the end electrodes with satisfactory peel strength and heat resistance sufficient to exhibit good resistance to soldering.
Accordingly, it would be highly desirable to develop a chip resistor of which end electrodes can be manufactured according to a thin film deposition technique and which is capable of operating with high reliability.